1. Field of the Invention
The present invention relates to a screw or fastener and to a driving tool to drive or withdraw such screw, the screw and driving tool being releasably coupled during operation.
2. Description of the Prior Art
A number of screw and screwdriver combinations are known in the prior art which are intended to overcome the problem of slip-out or displacement of the screwdriver and screw while endeavoring to drive the screw home, as well as while endeavoring to remove the screw. These problems can result in ruining the engagement slot provided in the screw head, damage to the bit of the screwdriver and present the possibility of injury to the user. In many cases, screws have been damaged beyond effective use, requiring replacement. In some cases the screwdriver itself was damaged beyond repair. Also, while attempting to remove prior art screws, the surrounding portions of the workpiece have, on occasion, splintered or become otherwise damaged, requiring costly repair.
U.S. Pat. No. 3,675,694, to Barlow, issued July 11, 1972, shows a screw having a screw head with laterally extending keyways. A companion screwdriver has mating keys which mate with the keyways of the screw during use to compensate for misalignment and eliminate bouncing of the blade of the screwdriver from the screw slot. It was necessary to maintain at least a minimum positive pressure between the screwdriver and screw to maintain the key and keyway engagement.
Similarly, the following U.S. Patents show prior art screws and screwdrivers, the screw head being provided with a uniquely shaped engagement opening for mating with the driving tool to assist in maintaining alignment of the screw and driving tool: U.S. Pat. Nos. 3,463,209; 4,037,514; 4,269,246; 4,128,038; and 3,888,144. The devices shown in each of these references require that at least a minimum driving pressure be exerted between the driving tool and screw to maintain the engagement thereof.
U.S. Pat. No. 3,695,321 to Garehime, Jr., issued Oct. 3, 1972, shows a cavity head screw and driving tool, the screw having undercut cavities and a central bore. The driving tool has multiple blades and a central pin which is received within the screw hole. The screwdriver blades mate with the undercut sidewalls of the screw cavity to align and axially stabilize the screwdriver and screw during operation.
In spite of the above advances, there exists a need for a screw and driving tool which maintains the screw and driving tool in a coupled state, even when no pressure is exerted to maintain the driving tool in working engagement with the screw.
The present invention has as its object to provide a screw and screwdriver combination with interlocking features for releasably coupling the screwdriver to the head of a mating screw to facilitate driving or removing the mating screw into or from a workpiece.
A further object of the invention is to provide a coupling mechanism between the screwdriver and mating screw which maintains the alignment of the screwdriver and the screw head to thereby prevent bounce, slip-out or displacement of the screwdriver from the screw.
Another object of the invention is to provide a screwdriver and mating screw which are positively coupled during use to provide greater turning power and less likelihood of slippage or accidental disengagement than was previously possible.
Additional objects, features and advantages will be apparent in the written description which follows.